Papers by Keyword: Strain Rate

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Authors: Wen Huang, Zhong Wei Huang
Abstract: A FEA model, based on the crystal plasticity theory, was established to study the mechanical behavior of titanium, and the microstructure evolution during deformation. Simulation on the dynamic tension of a commercially pure polycrystalline titanium at different strain rates and temperatures showed that the model can well describe the stress-strain behavior of titanium, the simulated results also revealed the contribution of different slip systems to the deformation of titanium, and the grain reorientation evolution caused by the crystallographic slipping.
Authors: En Yang Wang, Masaki Omiya
Abstract: A Microscopic Study on Local Strain Rate Sensitivity of Polypropylene Syntactic Foam with Microballoons
Authors: Yo Tomota, K. Ikeda, Mayumi Ojima, Junichi Suzuki, Takashi Kamiyama
Authors: Geun Su Joo, Min Kuk Choi, Hoon Huh
Abstract: The tension/compression hardening behavior is important in sheet metal forming processes because of complicated loading paths. Experimental methods to measure the tension/ compression behavior have not considered the effect of the strain rate although the strain rate is related to the hardening behavior of sheet metal. The tension/compression tests need to be conducted considering the strain rate to acquire accurate hardening behavior.This paper deals with an experimental technique to measure the tension/compression behavior of sheet metal at various strain rates. A new clamping device was developed to prevent a sheet specimen from buckling under compression loading condition. Compared to previous clamping devices, the clamping device was devised to uniformly impose a clamping force and easily measure the strain from side of a specimen. Tension/compression tests have been conducted at various strain rates for SPCC and DP590 with displacement of 10%. Hardening curves under the tension or compression loading condition were obtained and analyzed with respect to the strain rate.
Authors: Wen Huang, Zhong Wei Huang
Abstract: A statistical constitutive model, which takes account the effect of strain rate, was presented to describe the stress-strain relationship of brittle fiber bundles. To verify its reliability, tensile tests on two kinds of brittle fibers: glass fiber and SiC fiber, were carried out at different strain rates, and the stress-strain curves were obtained. It was found that the modulus E, the strength and the fracture strain of these fiber bundles all increase with increasing strain rate. The simulated stress-strain curves, derived from the constitutive model, fit the tested results well, which indicates that the model is valid and reliable.
Authors: Yashar Khalighi, Nemy Banthia
Abstract: Our understanding of how the bond between FRP and concrete performs under impact loading is severely limited. In this paper, bond performance of Sprayed FRP with concrete was studied under impact loading. A novel 550 mm × 150 mm × 150 mm notched specimen was developed and a 75 mm wide strip of Sprayed FRP was applied to strengthen the specimen. A novel test set-up designed to minimize the influence of specimen rebound after impact as well as eliminate the need to correct the load data for inertial effects was developed. FRP strains were measured using strain gauges carefully installed on the FRP, and the bond stress was calculated using the differential strain values. A kinematics analysis was also performed to translate the vertical deflections into strain values. Three types of surface preparation methods (water jetting, sand blasting, and jack hammering) were studied. Specimens are tested under four different strain rates (four different hammer heights of 250, 500, 750, and 1000 m) and the results were compared with quasi static values using loading rates of 0.005, 0.05, and 0.5 mm/min. Results showed that sand blasting is the most effective surface preparation method resulting in the highest bond strength values. Impact results were characterized using a Dynamic Improvement Factor (DIF). Results indicate that the FRP–concrete bond is highly strain sensitive, and in general the bond strength increases and the fracture energy decreases under higher rates of strain. Untreated specimens are shown to be more strain-rate sensitive than the surface treated ones.
Authors: Jia Qu, Guang Ping Zou
Abstract: Concrete is a type of engineering composites which is widely used in military and civil structures. The static performance of concrete can not be used to estimate the variation of concrete under high strain rates under dynamic loads. By introducing the three point bending test under static and dynamic loads, the plane strain fracture toughness KIC and KId were measured. Using the application of experimental-numerical method a three-dimensional model has been established by FEM software Ansys/LS-DYNA, to carryout transient analysis, and the response curves of stress intensity factor-time through the opening displacement of fracture. Thus, with obtaining the cracking time by the method of strain-gauge, the dynamic plane strain fracture toughness KId can be determined. By comparing KIc and KId we could conclude the result which meant concrete was more liable to crack under dynamic load.
Authors: P. Heurtier, Christophe Desrayaud, Frank Montheillet
Authors: Keitaro Horikawa, Kenichi Yoshida, Kiyoshi Sakamaki
Authors: Buddhisagar Naik
Abstract: Different models have been put forward to explain superplasticity. Most of the models predict the independency of activation energy (Q) on stress. Superplasticity is observed in region II of creep curve (logε Vs σ/E). The most commonly considered mechanism for superplastic flow involves Grain Boundary Sliding (GBS), and it is necessary for an accommodation process to accompany GBS. The accommodation process might be grain boundary migration, recrystalisation, diffusional flow or some dislocation slip process. But the Arrhenius type of equation given by Becker gives the dependency of activation energy on stress. Here in this work we have considered this equation and relation between Q and σ is found out using genetic algorithm. The present model development studies the parameter optimization, where parameters appearing in the stress and energy relationship equation e.g. relationship between Q(σ) and σ for the Q(σ) equation given in present work as well as pre-exponential factors are optimized with the objective function being the error minimization of model predicted values and experimental data of strain are available from open literature.
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